shall be in effect a written agreement of the lessor or owner or secured party of such airframe (which may be a lease or conditional sale or other security agreement covering such airframe) substantially similar in effect to the agreement of Lessor in Section 6(b) below whereby such lessor or owner or secured party effectively and expressly agrees that neither it nor its successors or assigns will acquire or claim any right, title or interest in any Engine by reason of such Engine being installed on such airframe at any time while such Engine is subject to this Lease, and a copy of such agreement shall be provided to Lessor and any Lessor Lender upon written request, provided, however, that the restriction contained in this clause shall not apply to the installation of an Engine on an airframe leased to Lessee or in the possession of Lessee subject to a conditional sale agreement or owned by Lessee subject to a security agreement for a period not to exceed sixty (60) days so long as Lessee installs a Replacement